FK506 By mbraaschturi Jan 1, 1980 1980 Mar 1, 1987 FK506 isolation Feb 1, 1989 Total synthesis by Merck Mar 1, 1990 Formal synthesis by Sih et al Apr 1, 1990 Formal synthesis by Danishefsky et al Jul 1, 1990 Total synthesis by Schreiber et al May 26, 1992 First US Patent held by Merck Jan 1, 1993 FK506 made industrially using 22nd generation bacteria Jan 1, 1994 FDA approval for liver transplants Apr 20, 1994 Formal total synthesis by Smith et al Oct 4, 1996 Total synthesis by Ireland et al Feb 1, 1997 Biosynthetic gene clusters identified Jul 22, 1997 Total synthesis by Ireland et al Jan 20, 1998 Formal synthesis routes proposed by Smith et al Jan 13, 2011 International Patent under Lek Pharmaceuticals Jan 1, 2015 2015